Corruption is thick as fleas on a fat dog in the Northern Canadian mining town of Elliot, so Reid Bennett, ex-chief of police of the town of Murphy's Harbor, takes a job in the local police force, going undercover to sort out who's been bad and who's been good in this nicely constructed tale that is part mystery, part thriller. It's a small, tough place; ``There's not a lot else to do in a town like Elliot except drink and punch one another out,'' observes Reid to his new wife, Freda, their first night there. He and his highly trained German shepherd, Sam, discover otherwise in the weeks that come as they spar with the sadistic sergeant of the police department and ponder the possibility of dishonesty right on up the line, uncovering drug dealing, prostitution payoffs, murder, arson and, in a tense, well-wrought finale, grand larceny. Wood ( When the Killing Starts ) has a nice ear for dialogue, and his outsize (for a mystery), satisfying plot really moves. (June)